1. Field of the Invention
This invention relates generally to the field of a method and apparatus for drilling of wells and more particularly to a downhole well drilling apparatus and method of use for enhancing rotary well drilling operations.
2. Background Art
Most well drilling operations are conducted by rotary operations in which extendible lengths of drill string having a drill bit mounted at the lower end thereof are rotated from the earth's surface or by a down hole motor. Rotation of the drill string rotates the drill bit for extending the bore hole deeper into the earth during such drilling operations.
To enhance such rotary well drilling operations, numerous tools have been developed for mounting and use at sub-surface locations in the drill string to enhance the drilling operation. One such tool is called a reamer and is used to slightly underream, enlarge, straighten the maintain gage of a bore hole. Reamers, which are sometimes also used as drill string stabilizers, are conventionally supplied with a plurality of rotatable cutting blade rollers on a tubular member that contact the wall of the bore hole for enlarging the bore hole or removing the undesired obstruction. In some instances the term reamers are also described as a down hole milling or scraping tool used to cut or remove wall cake from the casing. The term reamer, as used herein, is not intended to cover a milling type of tool or the use of such a down hole drilling tool for removing the casing or a mud cake within the casing.
According to the 1986-87 edition of the Composite Catalog of Oil Field Equipment and Services published by Gulf Publishing of Post Office Box 2608, Houston, Texas, reamer tools with reference to specific volumes and page numbers, are presently commercially available in many embodiments for use from the following suppliers:
______________________________________ REAMERS - Hole Opening: A-Z Int'l Tool Co. 146 V-1 C.P. Oil Tool Co. 865 V-1 Canamco Services & Supplies Int'l 695 V-1 Diamant Boart 1547 V-1 Drilco Division (Smith) 1748 V-1 Drillstar 1775 V-1 Driltrol 1800 V-1 Eastman Whipstock, Inc. 1873 V-2 Grant Tool Co. 2339 V-2 Haco Int'l Co. 2387 V-2 Industrialexportimport/Petromin 3603 V-3 S M F Int'l 5809 V-4 Security Division 5663 V-4 Texas Oil Tools, Inc. 6155 V-4 Tri-State Oil Tool Industries, Inc. 6263 V-4 Triumph-L O R, Inc. 4304 V-3 Wilson Industries, Inc. 6796 V-4 REAMERS - Jar & Key Seat: Bowen Tools, Inc. 555 V-1 Drilco Division 1764 V-1 Drillstar 1786 V-1 Driltrol 1800 V-1 Grant Oil Tool Co. 2344 V-2 Homco Int'l, Inc. 2689 V-2 Oilfield Mfg. Pte. Ltd. 5158 V-4 S M F Int'l 5819 V-4 Tri-State Oil Tool Industries, Inc. 6261 V-4 Wilson Industries, Inc. 6796 V-4 REAMERS - Rotary: Canamco Services & Supplies Int'l 695 V-1 Darron Oil Tools 1452 V-1 Diamant Boart 1533 V-1 Dreco Energy Services Ltd. 1696 V-1 Drilco Division 1743 V-1 Drillstar 1779 V-1 Driltrol 1800 V-1 Eastman Whipstock, Inc. 1874 V-2 Grant Oil Tool Co. 2324 V-2 Griffith Oil Tool Ltd. 2357 V-2 Industrialexportimport/Petromin 3603 V-3 Mento A/S 4487 V-3 Mid-Continent Supply Co. 4589 V-3 Oncor Products, Hughes Drilling Equip. 3027 V-2 S M F International 5806 V-4 Security Division 5663 V-4 Texas Oil Tools, Inc. 6155 V-4 Tri-State Oil Tool Industries, Inc. 6261 V-4 Triumph - L O R, Inc. 4298 V-3 Tsukamoto Seiki Co., Ltd. 6299 V-4 Wilson Industries, Inc. 6796 V-4 REAMERS - Stabilizing: Canamco Services & Supplies Int'l 695 V-1 Dreco Energy Services, Ltd. 1696 V-1 Drilco Division 1743 V-1 Driltrol 1800 V-1 Grant Oil Tool Co. 2324 V-2 Griffith Oil Tool Ltd. 2357 V-2 Haco Int'l 2387 V-2 Industrialexportimport/Petromin 3603 V-3 Oncor Products, Hughes Drilling Equip. 3028 V-2 S M F Int'l 5806 V-4 Security Division 5663 V-4 Triumph- L O R, Inc. 4298 V-3 Tsukamoto Seiki Co., Ltd. 6299 V-4 Wilson Industries, Inc. 6796 V-4 ______________________________________
U.S. Pat. No. 3,306,381 to Garrett, et al, which is assigned to the owner of Drilco, discloses a typical reaming tubular apparatus having a plurality of circumferentially spaced roller cutters mounted with hardened tungsten carbide cutting inserts externally protruding therefrom. The disclosed external bearings for the rollers are not sealed, although the use of sealed bearings is known and shown in the Drilco sales literature.
Another useful tool used in the drill string to enhance drilling operation is a stabilizer which contacts the bore hole wall and effectively serves as a radial bearing or lateral support for the rotating drill string in the bore hole. By holding the drill string against lateral forces or radial movement, the stabilizer serves to limit the unsupported column length of the drill string to prevent buckling as well as radial or lateral vibration, drill string diameter wear and the bending stress inducing movement of the drill string. In certain formations, a stabilizer also can be used enlarge the cylindrical bore hole side wall to a predetermined gauge or diameter. Stabilizers are usually formed by a tubular member with a plurality of outwardly extending fixed blades having wall contacting surfaces of hardened material that bear against or contact the sides of the borehole. The outwardly extending blades are usually mounted straight (vertical) or have a helical swirl. Various arrangements of mounting the blades, which may be field replaceable, also serve as a descriptive distinction of the types of various stabilizers.
The definition and use of stabilizers and reamers tend to overlap, but for purposes of distinguishing the two in this disclosure the term reamers will be limited to the rotatable cutting blade roller tools while stabilizers will be limited to rotating fixed blade tools.
The previously mentioned edition of the Composite Catalog also identifies the following suppliers of stabilizer tools:
______________________________________ STABILIZERS - Casing, Drill Pipe & Tubing: A-1 Bit & Tool Co. 103 V-1 Arai Iron Works Co., Ltd. 245 V-1 B J Products, Hughes Drilling Equipment 2955 V-2 Canamco Services & Supplies Int'l 695 V-1 Darron Oil Tools 1448 V-1 Grant Oil Tool Co. 2324 V-2 Haco Int'l Co. 2387 V-2 Industrialexportimport/Petromin 3603 V-3 Mento A/S 4487 V-3 Oncor Products, Hughes Drilling Equipment 3030 V-2 Petco 5401 V-4 S.E.A. Supply Co., Inc. 2209 V-2 S M F Int'l 5798 V-4 STABILIZERS - Clamp on: Drilco Division 1764 V-1 Reed Tool Co. 5525 V-4 S M F Int'l 5801 V-4 STABILIZERS - Cushion: Chimo Polyurethanes Ltd. 1279 V-1 Driltrol 1802 V-1 Grant Oil Tool Co. 2328 V-2 STABILIZERS - Diamond: B J Products, Hughes Drilling Equipment 2969 V-2 Diamant Boart 1551 V-1 J. K. Smit & Sons Diamond Tools Ltd. 5757 V-4 STABILIZERS - Drill Collar: Silvio Ballerini & C. S.P.A. 387 V-1 Bowen Tools, Inc. 512 V-1 Canamco Services & Supplies Int'l 695 V-1 Cutting & Wear Resistant Developments 1349 V-1 Darron Oil Tools 1448 V-1 Diamant Boart 1551 V-1 Drilco Division 1732 V-1 Driltrol 1801 V-1 Grant Oil Tool Co. 2325 V-2 Haco International Co. 2387 V-2 Hendershot Tool Co. 2654 V-2 Industrialexportimport/Peromin 3603 V-3 O K G T 5123 V-4 Oncor Products, Hughes Drilling Equipment 3030 V-3 Reed Tool Co. 5525 V-4 S M F International 5799 V-4 Teleco Oilfield Services, Inc. 6051 V-4 Triumph - L O R, Inc. 4290 V-3 Tsukamoto Seiki Co., Ltd. 6298 V-4 Vereinigte Edelstahlwerke V E W 6481 V-4 Walker - Neer Manufacturing Co., Inc. 6618 V-4 Wilson Industries, Inc. 6792 V-4 STABILIZERS - Free Wheeling: A-1 Bit & Tool Co. 103 V-1 A-Z International Tool Co. 145 V-1 Drilstar 1786 V-1 Oncor Products, Hughes Drilling Equipment 3031 V-2 Triumph - L O R, Inc. 4296 V-3 STABILIZERS - Integral Blade: Bowen Tools, Inc. 512 V-1 Canamco Services & Supplies Int'l 695 V-1 Christensen, Inc. 5047 V-3 Cutting & Wear Resistant Developments 1349 V-1 Dailey Petroleum Services Corp. 1364 V-1 Darron Oil Tools 1448 V-1 Diamant Boart 1551 V-1 Dreco Energy Services Ltd. 1696 V-1 Drilco Division 1735 V-1 Drillstar 1776 V-1 Driltrol 1802 V-1 Eastman Whipstock, Inc. 1869 V-2 Grant Oil Tool Co. 2330 V-2 Griffith Oil Tool Ltd. 2357 V-2 Haco Int'l Co. 2387 V-2 Hunting Oilfield Services Ltd. 3200 V-2 Norton Christensen, Inc. 5047 V-3 Oilfield Mfg. Pte. Ltd. 5154 V-4 Oncor Products, Hughes Drilling Equip. 3034 V-2 Reed Tool Co. 5525 V-4 S M F International 5797 V-4 Security Division 5663 V-4 Triumph - L O R, Inc. 4290 V-3 Tsukamoto Seiki Co., Ltd. 6298 V-4 Vereinigte Edelstahlwerke V E W 6481 V-4 Walters Oil Tool Machine Ltd. 6628 V-4 Wilson Industries, Inc. 6796 V-4 STABILIZERS - Mill: Cutting & Wear Resistant Developments 1349 V-1 Darron Oil Tools 1448 V-1 Driltrol 1802 V-1 Tri-State Oil Tool Industries, Inc. 6261 V-4 Wilson Industries, Inc. 6796 V-4 STABILIZERS - Non-Magnetic: Christensen, Inc. 5048 V-3 Cutting & Wear Resistant Developments 1349 V-1 Darron Oil Tools 1450 V-1 Diamant Boart 1551 V-1 Norton Christensen, Inc. 5048 V-3 Reed Tool Co. 5525 V-4 SMF International 5796 V-4 Teleco Oilfield Services Inc. 6051 V-4 Tirumph-LOR, Inc. 4290 V-3 Vereinigie Edelstahlwerke VEW 6481 V-4 Wilson Industries, Inc. 6796 V-4 STABILIZERS - Packed Hole Assemblies: Christensen, Inc. 5045 V-3 Diamant Boart 1551 V-1 Draco Energy Services Ltd. 1696 V-1 Driico Division 1732 V-1 Driltrol 1801 V-1 Grant Oil Tool Co. 2324 V-2 Norton Christeneen, inc. 5045 V-3 Oncor Products, Hughes Drilling Equipment 3026 V-2 SMF International 5797 V-4 Security Division 5663 V-4 Vereinigte Edelstahlwerke VEW 6481 V-4 Wilson Industries, Inc. 6796 V-4 STABILIZERS - Pulsation: Fluid Kinetics Corp. 1955 V-2 Holthuis B.V./GEHO 2667 V-2 Joy Petroleum Equipment Group 3773 V-3 STABILIZERS - Replaceable Pad: Drilco Division 1732 V-1 Grant Oil Tool Co. 2329 V-2 Oncor Products, Hughes Drilling Equipment 3034 V-2 SMF International 5800 V-4 Triumph-LOR, Inc. 4299 V-3 STABILIZERS - Rubber: BJ Products, Hughes Drilling Equipment 2953 V-2 Chimo Polyurethanes Ltd. 1279 V-1 Drilco Division 1740 V-1 Drillstar 1778 V-1 Driltrol 1802 V-1 Grant Oil Tool Co. 2328 V-2 Regal International, Inc. 5573 V-4 SMF International 5803 V-4 Triumph-LOR, Inc. 4296 V-3 Vereinigte Edeistahlwerke VEW 6481 V-4 STABILIZERS - Sleeve: Canamco Services & Supplies International 695 V-1 Chimo Polyurethanes Ltd. 1279 V-1 Christensen, Inc. 5049 V-3 Cutting & Wear Resistant Developments 1351 V-1 Darron Oil Tools 1449 V-1 Diamant Boart 1551 V-1 Drilco Division 1735 V-1 Drillstar 1776 V-1 Driltrol 1801 V-1 Eastman Whipstock, Inc. 1867 V-2 Grant Oil Tool Co. 2331 V-2 Haco International Co. 2387 V-2 Norton Christensen, Inc. 5049 V-2 Oilfield Mfg. Pte. Ltd. 5167 V-4 Oncor Products, Hughes Drilling Equipment 3031 V-2 Reed Tool Co. 5525 V-4 SMF International 5798 V-4 Security Division 5663 V-4 Tri-State Oil Tool Industries, inc. 6261 V-4 Triumph-LOR, Inc. 4296 V-3 Tsukamoto Seild Co., Ltd. 6298 V-4 Vereinigte Edeistahlwerke VEW 6481 V-4 STABILIZERS - Spiral Blade Bowen Tools, Inc. 512 V-1 Canamco Services & Supplies International 695 V-1 Cutting & Wear Resistant Developments 1349 V-1 Darron Oil Tools 1448 V-1 Diamant Boart 1551 V-1 Dreco Energy Services Ltd. 1696 V-1 Drilco Division 1735 V-1 Drillstar 1776 V-1 Driltrol 1802 V-1 Grant Oil Tool Co. 2324 V-2 Griffith Oil Tool Ltd. 2357 V-2 Haco International Co. 2367 V-2 Industrialexportimport/Petromin 3603 V-3 Oncor Products, Hughes Drilling Equipment 3030 V-2 Reed Tool Co. 5525 V-4 SMF International 5797 V-4 Security Division 5663 V-4 Tri-State Oil Tool Industries, Inc. 6261 V-4 Triumph-LOR, Inc. 4290 V-3 Vereinigte Edeistahlwerke VEW 6481 V-4 Wilson Industries, Inc. 6796 V-4 STABILIZERS - Suction: Joy Petroleum Equipment Group 3773 V-3 STABILIZERS - Turbo Lift: Darron Oil Tools 1448 V-1 Datadril Division 1453 V-1 STABILIZERS - Welded Blade: A-1 Bit & Tool Co. 103 V-1 Bowen Tools, Inc. 512 V-1 Darron Oil Tools 1448 V-1 Dreco Energy Services Ltd. 1696 V-1 Drilco Division 1742 V-1 Drillstar 1776 V-1 Driltrol 1802 V-1 Eastman Whipstock, Inc. 1868 V-2 Grant Oil Tool Co. 2330 V-2 Griffith Oil Tool Ltd. 2357 V-2 Haco International Co. 2367 V-2 Hendershot Tool Co. 2654 V-2 Oilfield Mfg. Pte. Ltd. 5167 V-4 SMF International 5797 V-4 Tri-State Oil Tool Industries, Inc. 6261 V-4 Triumph-LOR, Inc. 4294 V-3 Tsukamoto Seild Co., Ltd. 6296 V-4 Wilson Industries, Inc. 6796 V-4 ______________________________________
U.S. Pat. No. 3,680,647 to Dixon and Crews, which is also assigned to the owner of Drilco, discloses a square drill collar type fixed blade stabilizer used for drill bit stabilization and deviation control. As noted therein, stabilizers can be further characterized as non-rotating or rotating. The so called non-rotating types employ a fixed well bore wall protective sleeve member which is rotatably mounted on the drill stem attached stabilizer body and for purposes of the patent invention will be considered a fixed blade stabilizer. Crews combines a fixed blade stabilizer and drill collar in a single tool equipped with field replaceable vertical wear blades received in specially formed longitudinally extending grooves. Such tool is also disclosed in Drilco's "RWP" or replaceable wear pad stabilizer sales literature.
Of particular interest is the prior art illustration of FIG. 1 of the patent which shows six different drill string mounting arrangements of various individual separate downhole drilling tools such as non-rotating stabilizers, a roller cutter reamer--stabilizer, fixed blade rotary stabilizers and square drill collars above the drill bit. Each individual tool performs a separate function independent of the others and requires make-up of two threaded connections in the drill string. As the threaded connections are weak points and subject to failure they are necessary, but undesirable.
In U.S. Pat. No. 3,754,609 to Garrett (also Drilco) a flexible threaded end connector is disclosed for use with reamer--stabilizer of the fixed helical blade type with the blades formed on a replaceable sleeve. The flexible connector attempted to protect the threads by preventing leakage and providing proper torque transfer when the drill string is subjected to buckling or bending from compressive loading.
In U.S. Pat. No. 4,428,626, to Blau et al, a releasable mounting arrangement for hardened well contacting inserts or blades to a stabilizer is disclosed. A closed end undercut vertical slot or groove is formed on the tool with a central full non-undercut release opening for the slot. A retainer block having a plurality of spring loaded detents is secured in the opening to maintain the wear pads locked into the groove. Additional back up friction lock means may be provided if desired. In FIG. 13, an undercut groove embodiment for mounting a longitudinally spaced pair of non-lubricated mounting blocks for a roller cutter reamer tool is disclosed.
U.S. Pat. Nos. 3,773,359 and 3,784,238 discloses an intermediate drill stem used to distribute the bending load from the stiff heavy drill collars used to weight the drill bit to the more flexible drill pipe and in which the threaded end connections are made more rigid than the body to preferentially bend the body. The stronger ends are intended to protect the weaker make up threads from plastic deformation due to excessive stress loading from drill string bending stresses induced during operation. The longitudinally spaced protective collars are hardened to prevent excessive wear from contact with the bore hole wall.
U.S. Pat. No. 3,818,999 to Garrett discloses a rotating fixed blade stabilizer of the square drill collar type. The field replaceable hardened wear inserts are received in the 90.degree. angled vertically extending grooves and are secured therein by bolting.
A third type of useful tool used in the drill string to enhance drilling operation is a shock absorber tool which is preferably run connected directly to the drill bit and below the drill collars. This longitudinally telescoping tool is intended to dampen out the vibration and axial movement of the drill bit resulting from the rotational movement of the drill bit which excites or vibrates the drill string. The shock absorber's primary purpose is to maintain the cutting edge of the drill bit in optimum cutting contact with the formation at all times.
The shock absorbing tool should be contrasted with the bumper sub which is a slip-joint tool that is used in the string of drill pipe when drilling from a floating vessel to absorb the vertical motion of the vessel caused by wave action. The bumper sub slip-joint is inserted above the heavy drill collars in order to maintain the weight of collars on the drill bit as the drill pipe above the slip-joint moves up and down with the motion of the vessel. The bumper sub is also a term used in fishing operations to describe and identify a tool that imparts a jarring action to the fishing string to help free the "fish". The shock absorber tool is also not to be confused with the drilling jar tool which is used to deliver a jarring impact to free a drill string stuck in the bore hole as disclosed in U.S. Pat. No. 4,284,153 to Reaugh.
The drilling shock absorbing tool is generally formed of two tubular assemblies secured in a relatively movable longitudinal telescoping relationship and which are splined or otherwise restrained to prevent relative circumferential rotation. A resilient vibration dampening means is operably connected between the two tubular assemblies to absorb and virtually eliminate the variable dynamic loading on the drill bit. Dampening is usually provided by mechanical springs, trapped fluid and or gas, resiliently deformable rubber members or combinations thereof which resist the axial compressive stroke. To be most effective the shock absorber is run immediately above the drill bit and below the drill collars. The stability or stiff column characteristics of the shock absorber tool is adversely affected by the necessity for the longitudinal operating stroke or telescoping movement which usually results in a bending resistant weak point in the drill collar portion of the string. As this weakness can result in uncontrolled deviation of the borehole direction it is highly undesirable. Prior efforts to correct this weakness have not been commercially successful or accepted with serious reservations.
The Composite Catalog 1986-87 edition lists the following Drilling Tool Shock Absorber suppliers:
______________________________________ ABSORBERS - Shock, Drilling: ______________________________________ B J Products, Hughes Drilling Equip. 3036 V-2 Bowen Tools, Inc. 563 V-1 Brown Products, Hughes Production Tools 3047 V-2 Canamco Services & Supplies Int'l 695 V-1 Christensen, Inc. 5042 V-3 Cougar Tool 1315 V-1 Dailey Petroleum Services Corp. 1360 V-1 Dreco Energy Services Ltd. 1692 V-1 Drilco Division 1751 V-1 Griffith Oil Tool Ltd. 2357 V-2 Hawn Tool Co. 2662 V-2 Hunt Oil Tool Co. 3219 V-2 Jarco Services, Inc. 3692-3 V-3 Mento A/S 4487 V-3 Norton Christensen, Inc. 5042 V-3 Positive Action Tool 5453 V-4 Security Division 5664 V-4 Swaco Division 5945 V-4 Triumph - L O R, Inc. 4288 V-3 ______________________________________
U.S. Pat. Nos. 3,660,990 to Zerb, et al and 3,774,731 to Zerb alone disclose shocker absorber tools and are both entitled "Vibration Damper". Both patents now owned by the owner of the present invention employ a rubber elements as a resilient dampening means.
U.S. Pat. No. 3,099,918 to Garrett (Drilco) discloses a telescopic shock absorber tool preferably run between the drill bit and the drill collars to dampen vibrations and impacts induced by the drill bit. A rubber resilient sleeve is employed as the dampening mechanism. U.S. Pat. No. 3,254,508 was also granted to Garrett for a shock absorber tool using a unique corrugated metal spring for resiliency. Garrett U.S. Pat. No. 3,447,340 is an improvement of the shock absorber metal spring formed with helical grooves to improve useful spring life.
U.S. Pat. No. 4,428,443 to Oliphant identifies and classifies by resilient member a number of prior art patents as well as disclosing a slotted metal spring member. U.S. Pat. No. 4,443,206 to Teng also discloses a shock absorber well tool in which a rubber resilient element is employed as well as a unique helical spline means.
U.S. Pat. No. 4,211,290 to Mason, et al discloses a shock absorbing tool having a deformable element formed by a stack of alternate layers of non-deformable metal washer and deformable elastomer rings. The deformable element is protected in an oil bath filled expansible chamber having a floating piston to equalize the sealed oil bath pressure with the internal drilling fluid pressure. By equalizing these pressures, undesired preloading of the resilient element by the hydrostatic head is avoided.
Three types of prior art shock absorbers are identified in the background of the invention of the Mason patent.
In the first type, the telescoping tubular sections are sealed in such a manner that internal well fluid hydrostatic pressure urges against the resilient or deformable element used to expand the tubular sections. Under deep well operating conditions the hydrostatic pressure "pre-loading" action overcomes even a "hard" deformable element. In those circumstances, the deformable element is essentially rigid and the shock absorber tool rendered ineffective.
In a second type of tool, the telescoping elements are sealed with a floating piston to equalize the chamber internal pressure and the hydrostatic pressure. Hard, compressible metal wire elements disposed in the chamber are used to resist the compressive loading on the tool.
A third type provides a relatively "soft" resilient element in a sealed chamber that is pressure equalized. A gas pressure zone is provided in the chamber as a resilient element which results in a soft spring type urging at shallow drilling depths and a hard spring type urging at deeper depths.
A characteristic of most shock absorbing tools is that the spring rate of the resilient element increases as the compressive loading increases. FIG. 15 of the Mason patent illustrates such relationship in graph form and describes the spring rate (average) as the load required to deflect the spring a total of one inch (2.54 cm). The spring characteristic curve for "soft", "moderate" and "hard" deformable resilient elements are plotted.
The Mason patent invention attempted to overcome the hydrostatic preloading problem using a pressure equalized annular expansible chamber containing the deformable element. Desirably, the resilient element does not contact the side walls of the expansible chamber and is formed of a layered stack of annular segments of non-deformable steel rings and deformable elastic rings arranged in alternating sequence. Such arrangement distributes the axial shock load uniformly throughout the length of the resilient element.
Mason, et al, is also concerned with the problem of lack of lateral rigidity in a shock absorber which may cause undesired bore hole deviation and high spline wear. However, no lateral support means for the shock absorber is disclosed.
The Maurer Engineering, Inc., 2916 West T.C. Jester, Houston, Texas 77018, undated shock absorber sales literature discloses a relatively short sub designed to be run immediately above the bit having a pressure balanced expansible chamber in which a Belleville spring resilient means located. Use of soft, medium and hard spring arrangements are disclosed to meet anticipated operating axial shock loads. The catalogue further suggests a combination stabilizer/shock absorber tool can be custom tailored if desired for specific applications, but contains no such disclosure.
With this helpful background category of the various types of shock absorber tools a brief review of the Composite Catalog suppliers is greatly simplified.
The Griffith Oil Tools, 4600 Post Oak Place, Houston, Texas 77027, 1982-83 Catalog shows two shock tools at pages 3706-3709. The embodiment illustrated at page 3707 shows resilient springs in an oil filled chamber. The tool is pressure balanced to keep the tool from closing in response to hydrostatic pressure. The Griffith export shock tool embodiment disclosed at page 3709 is substantially identical and provided with higher spring rates and shorter spline, but is not field repairable. Note the recognition of the desirability to run such tools immediately above the drill bit to minimize the oscillating mass being dampened by the tool.
The Trumph--LOR type Z Dampening Sub at page 4288 of the Composite Catalog employs on all metal resilient springs in an oil bath chamber having a floating piston arrangement which compensates for thermal expansion of the oil filled chamber and downhole hydrostatic pressure. A two stage resilient system employing metal ring springs is disposed in the chamber. One stage of springs is provided with a soft spring constant while the other stage provides a hard spring constant to ensure proper operation through a wide range of bit weights.
The long stroke Bowen Cushion Sub disclosed at page 1301 of the Composite Catalog also utilizes an oil filled chamber housing the "low spring rate" resilient member.
The Drilco steel spring "Shock Sub" disclosed at pages 2792 and 2793 employs a helical bellows-type spring that is more fully disclosed in the Garrett patents mentioned above.
The Hawn Tool Company shock absorber tool disclosed at page 4076 employs a preselected size floating piston orifice and a check valve to control the transferred of the trapped hydraulic fluid between sealed chambers. A seal failure renders the tool inoperative.
The Schlumberger shock absorber tool material (page 5005) discloses a hydraulically balanced tool having a constant rate metal spring disposed in the oil filled dampening chamber. Protected involute splines are used to reduce bearing contact pressure while providing high torsional strength. Note the typical suggested running relationship directly above the bit or between reamers and/or stabilizers for stabilization.
The Christensen "Shock-Eze" shock absorber tool (page 2028) employs a set of stacked Belleville springs as the resilient elements in an oil filled and sealed chamber. The long (5 in.) stroke enables the preloaded metal spring to operate in both directions.
The Security Dresser shock absorber displayed at Composite Catalog page 2704 employs a pressure balanced sealed chamber in which a metal Belleville spring arrangement provides the resilient element.
The Bat-Jac shock absorber at page 419 also provides a Belleville metal spring stack that is reinforced by fluid pressure.
The foregoing patents and publications are fully incorporated herein by specific reference for any and all purposes. Such listing of patents and publications is presented as neither exhaustive or comprehensive, but rather as representative of the known material prior art.